History: Water-storage tank owners and operators are aware of the need to properly maintain these critical components of their water system and have looked to the American Water Works Association (AWWA) for guidance on inspection and cleaning of tanks. The first AWWA tank inspection standard was AWWA D101-53, Standard for Inspecting and Repairing Steel Water Tanks, Standpipes, Reservoirs, and Elevated Tanks, for Water Storage. In 1998, AWWA Manual M42, Steel Water-Storage Tanks, was published as a guidance document. The handbook Steel Water Storage Tanks: Design, Construction, Maintenance, and Repair was published in 2010 by McGraw Hill in conjunction with AWWA.
Inspection Recommendations: AWWA recommendations, call for water-storage tanks to be professionally inspected at intervals not more than every 5 years.
Cleaning: Prior to conducting a field evaluation, it is recommended that the sediment be removed from the tank.
Inspections: The dry evaluation is the most thorough evaluation since all the tank surfaces are visible. Underwater evaluations of tank interiors are an alternative when tanks cannot be drained.
New AWWA D101: Practices and technology have evolved since the standard was published in 1953. The new standard doesn’t just apply to water-storage tanks, but also to related structures such as Aldrich units, clarifiers, clearwells, filter beds, and hydropneumatic tanks along with more traditional styles of tanks including bolted and welded steel structures.